import turtle
turtle.speed(0)
turtle.delay(0)
turtle.tracer(False)
i=-70
while(i<=110):
    i=i+0.1
    turtle.penup()
    y = 0.02*(i-20)*(i-20)+50
    turtle.goto(i,y)
    turtle.pendown()
    turtle.dot(4)
turtle.penup()
turtle.goto(0,0)
turtle.pendown()
turtle.seth(90)
turtle.fd(230)
turtle.seth(-70)
turtle.fd(15)
turtle.penup()
turtle.goto(0,230)
turtle.pendown()
turtle.seth(-110)
turtle.fd(15)
turtle.penup()
turtle.goto(0,235)
turtle.pendown()
turtle.write("y",True,align="center")
turtle.penup()
turtle.goto(0,0)
turtle.pendown()
turtle.seth(-90)
turtle.fd(90)
turtle.penup()
turtle.goto(0,0)
turtle.pendown()
turtle.seth(0)
turtle.fd(150)
turtle.seth(-160)
turtle.fd(15)
turtle.penup()
turtle.goto(150,0)
turtle.pendown()
turtle.seth(160)
turtle.fd(15)
turtle.penup()
turtle.goto(160,0)
turtle.pendown()
turtle.write("x",True,align="center")
turtle.penup()
turtle.goto(0,0)
turtle.pendown()
turtle.seth(-180)
turtle.fd(150)
turtle.penup()
turtle.goto(0,-120)
turtle.write("一元二次方程图像:y = 0.02*(x-20)^2+50",True,align="center")
turtle.goto(0,-300)
turtle.done()